A screw is a fastener commonly used in an industrial industry, an electrical industry, a medical industry, a construction industry and other industries. The screw may tightly lock a screw cap or other items; however, when the screw is difficult to be unscrewed, a simple operation may cause big difficulty; sometimes, the screw may be removed only when the item is damaged. Currently, a commonly used screw cap groove is “I-shaped”, “cross-shaped”, an inscribed hexagon, a quincunx and so on, the most common reason why these screws are difficultly unscrewed is that a screwdriver head slips in a screw cap groove, there are several following slipping reasons: 1) the screw cap groove has been damaged before the screw is screwed in; 2) because the screw has been retained for a long time and become rusted, or due to other reasons, the screw is required to overcome bigger resistance to be unscrewed, and hence the possibility of screw slippage increases; 3) the operator fails to rotate the screwdriver around a screw shaft due to improper operation so that the screw is taken off when being unscrewed, therefore, the screw cap groove is damaged, resulting in slippage. If the screw is slipped, it will be difficult to be unscrewed immediately, if the operator wants to unscrew the screw, not only it consumes time and labor, but also the screw cannot be unscrewed ultimately. It is thus obvious that the slippage caused when the screw is unscrewed has become a problem to be solved urgently. So far, there is no way to effectively solve the problem of screw slippage.